Tamarisk biocontrol, endangered species risk and resolution of conflict through riparian restoration

Abstract

A long-standing debate between wildlife agencies and biological control researchers and practitioners concerns Diorhabda carinulata Desbrochers (Coleoptera: Chrysomelidae) introduced to suppress invasive Tamarix spp. (Tamaricaceae), and potential impacts of Tamarix defoliation on endangered southwestern willow flycatchers using this non-native plant as nesting habitat in some western riparian ecosystems. The conflict and ensuing legal actions are currently centered on the presence of D. carinulata within the breeding range of the flycatcher in the Virgin River watershed, which has led to APHIS termination of permits supporting the biocontrol development program and has also affected other programs to develop biocontrol agents against environmental weeds. Central to concerns over wildlife is the lack of rehabilitation of native vegetation where biocontrol is expected, so there are current and planned efforts to promote restoration of native cottonwood-willow habitat to mitigate the anticipation decline in Tamarix cover. A strategic approach to riparian restoration is outlined which could facilitate sustainable, and scientifically documented recovery of this iconic habitat type. While the results of these efforts will not be known immediately, the process which is leading to riparian restoration has brought specialists from both sides of the debate together in search of resolution via collaboration, and if successful, may allow re-initiation of the Tamarix biocontrol program attendant with habitat enhancement for wildlife species of conservation concern.

Endangered species management and ecosystem restoration: finding the common ground

“…Because of this conflict, salt cedar eradication has been delayed while other control strategies are devised (U.S. Fish and Wildlife Service 1997). Without restoration efforts that assure the re-establishment of native riparian vegetation and restoration of ecosystem function, the removal of invasive salt cedar will result in a loss of nesting habitat for the endangered flycatcher (Zavaleta et al 2001, Dudley and DeLoach 2004, Sogge et al 2008, Dudley and Bean 2012.…”

Gene drives and the management of agricultural pests

“…Due to this and the likelihood of local gene drives spreading beyond their intended area of action, their regulation should require public discussion and, when appropriate, international agreements. For example, salt cedar is considered a pest by landowners but a valuable tree by wildlife protection groups (Dudley and Bean 2012). Similarly, prickly pear is considered a pest in Caribbean countries but a valuable plant in Mexico (Zimmermann, Klein, and Bloem 2004;Zimmermann, Bloem, and Klein 2007).…”

Mass Rearing of the Stem-Galling Wasp Tetramesa romana, a Biological Control Agent of the Invasive Weed Arundo donax

“…A key example is saltcedar (Tamarix spp. ), which has been controlled over wide areas using the biological method (Carruthers et al, 2008;Dudley and Bean, 2012). There is little commercial incentive to mass produce insects as weed biological control agents in noncrop areas.…”